This application incorporates by reference Taiwanese application Serial No. 090112560, filed May 24, 2001.
1. Field of the Invention
The invention relates in general to a driving apparatus and a method thereof, and in particular, to the apparatus for driving the address electrode of the plasma display panel and the method thereof.
2. Description of the Related Art
With the rapid developments in the fabrication technology of the audio/video (A/V) device, it can be foreseen that people in the future will enjoy the audio and video service with much higher performance than now. Taking the display device as an example, the conventional cathode ray tube (CRT) display device has the disadvantages of large volume, serious radiation issue, and serious image contortion and distortion at the brim region of the screen. Therefore, the conventional CRT display device certainly cannot satisfy the people who desire to enjoy the audio and video service with higher performance. When the high definition digital television (HDTV) system starts to operate and broadcast in the near future, the conventional CRT display device designed in the analog manner will gradually be obsolete. Instead, the plasma display panel (PDP), which has at least the advantages of low radiation, low power consumption, and large display area with small volume, can be a very promising product to replace the CRT display device.
FIG. 1 shows the diagram of the discharge unit of the tri-electrode alternating current plasma display panel (AC PDP). A plasma display panel includes n Y electrodes Y1xcx9cYn, n X electrodes coupled to each other, and m address electrodes A1xcx9cAm. Each Y electrode is parallel to each X electrode respectively. A pair of the X electrode and the Y electrode is orthogonal to an address electrode to form a discharge unit, as shown in FIG. 1. Therefore, the plasma display panel includes nxc3x97m discharge units. Each discharge unit can be lighted independently.
FIG. 2 shows the cross-sectional view of one discharge unit of the tri-electrode alternating current plasma display panel (AC PDP). Each discharge unit includes an X electrode, a Y electrode and an address electrode A. The X electrode and the Y electrode are set on the front glass substrate 202 in parallel and covered by the dielectric layer 204. The dielectric layer 204 is used for accumulating wall charges. The dielectric layer 204 is covered by the protective layer 206. The protective layer 206 is used for protecting the X electrode, the Y electrode, and the dielectric layer 204. The address electrode A is set on the back glass substrate 208 opposite to the front glass substrate 202, and is orthogonal to the X electrode and the Y electrode respectively. The address electrode A is covered by the fluorescence layer 210. The rib 212 is formed along the sides of the address electrode A. The space between the protective layer 206 and the fluorescence layer 210 is the discharge space 214. The discharge space 214 is filled with the discharge gas which comprises Ne and Xe.
The disadvantages of the plasma display panel are that the power loss is huge and the electromagnetic interference (EMI) problem is serious when switching the voltage of the address electrode by the address electrode driving apparatus. There are three kinds of conventional address electrode driving apparatus called the address electrode driving apparatus, the hard switching apparatus, and the bootstrap driving apparatus respectively. Each of them will be described in the following article.
FIG. 3 shows the diagram of the conventional address electrode driving apparatus for driving the address electrode of the plasma display panel 300. The conventional address electrode driving apparatus 300 comprises four switches (M1, M2, M3, and M4), two diodes (D1 and D2), a capacitor (Cs), and an inductance (L), as shown in FIG. 3. An external power source is coupled to the conventional address electrode driving apparatus 300 for applying the driving voltage Vd. A signal control apparatus 302 is coupled to the conventional address electrode driving apparatus 300 at the node a. The plasma display panel 304 is coupled to the signal control apparatus 302. The plasma display panel is represented in the form of the equivalent circuit 304 in FIG. 3. The equivalent circuit of the plasma display panel 304 includes the equivalent capacitor between the X electrode and the address electrode Cx, the equivalent capacitor between the Y electrode and the address electrode Cy, and the equivalent capacitor between the X electrode and the Y electrode Cxy, as shown in FIG. 3.
FIG. 4 shows the timing chart of the gate to the source voltage (Vgs) of M1 (Vg1), M2 (Vg2), M3 (Vg3), and M4 (Vg4), respectively, and the voltage of the node a (Va). When applying the gate to the source voltage Vgs to the gate electrode of the switch, the switch can be turned on. And when the gate to the source voltage Vgs does not apply anymore, the switch can be turned off. The operation of the conventional address electrode driving apparatus 300 can be controlled by controlling the ON and the OFF stages of the switches M1, M2, M3, and M4 periodically. The operation of the conventional address electrode driving apparatus 300 can be divided in 5 stages according to the stage of the switches M1, M2, M3, and M4 in one period. Each stage will be described in the following article.
When 0xe2x89xa6txe2x89xa6t1:xe2x80x83xe2x80x831.
When t=0, the switch M2 can be turned on and the other switches are turned off. The node a is coupled to the ground when the switch M2 is turned on. Therefore, the node a voltage Va is 0. After t=0, the switch M2 is turned off, and the voltage of node a remains 0.
When t1xe2x89xa6txe2x89xa6t2:xe2x80x83xe2x80x832.
When t=t1, the switch M3 can be turned on and the other switches are turned off. FIG. 5a shows the equivalent circuit of the conventional address electrode driving apparatus 300 when the switch M3 is turned on and the switches M1, M2, and M4 are turned off. The equivalent circuit of the plasma display panel 304 can be represented in the form of an equivalent capacitor Cp in FIGS. 5a and 5b. The capacitor voltage of the capacitor Cs is Vs. The capacitance of the capacitor Cs is much larger than the capacitance of the equivalent capacitor Cp. Therefore, the capacitor Cs can be regarded as a voltage source with a voltage Vs. When the switch M3 is turned on, a current I1 can flow from the capacitor Cs to the capacitor Cp through the inductance L. The capacitor Cp is charged by the current I1 and the node a voltage Va can be raised when the switch M3 is turned on, as shown in FIG. 4.
xe2x80x83When t2xe2x89xa6txe2x89xa6t3:xe2x80x83xe2x80x833.
When t=t2, the voltage of node a is Vd and the switch M1 can be turned on. When the switch M1 is turned on, the node a is coupled to the external power source directly. Because the magnitude of the node a voltage and the applying voltage of the external power source is equaled when the switch M1 is turned on, there is no current between the external power source and the node a. Therefore, the voltage of node a is still Vd.
When t3xe2x89xa6txe2x89xa6t4:xe2x80x83xe2x80x834.
When t=t3, the switch M4 can be turned on and the other switches are turned off. FIG. 5b shows the equivalent circuit of the conventional address electrode driving apparatus 300 when the switch M4 is turned on and the switches M1, M2, and M3 are turned off. When the switch M4 is turned on, the capacitor Cp will be discharged and a current I2 will flow from the capacitor Cp to the capacitor Cs through the inductance L. The capacitor Cp can be in resonance with the inductance L. Therefore, the node a voltage can be lowered. When switching the voltage of the address electrode, the power is stored by the resonance between the capacitor and the inductance. In this manner, the power loss of the plasma display panel can be decreased.
When txe2x89xa7t4:xe2x80x83xe2x80x835.
When t=t4, the voltage of node a is lowered to 0 and the switch M2 can be turned on again.
In this manner, the operation of the conventional address electrode driving apparatus 300 in one period has been accomplished.
FIG. 6 shows the diagram of the conventional hard switching apparatus for driving the address electrode of the plasma display panel 600. The conventional hard switching apparatus 600 includes 2 switches (M1, and M2) and a resistor (R). An external power source is coupled to the conventional hard switching apparatus 600 for applying the driving voltage Vd. A signal control apparatus 602 is coupled to the conventional hard switching apparatus 600 in the node a. The plasma display panel 604 is coupled to the signal control apparatus 602. The plasma display panel is represented in the form of the equivalent circuit 604 in FIG. 6.
FIG. 7 shows the timing chart of the gate to the source voltage (Vgs) of M1 (Vg1), and M2 (Vg2), respectively, and the voltage of the node a (Va). The operation of the conventional hard switching apparatus 600 can be controlled by controlling the ON and the OFF stage of the switches M1 and M2 periodically. The operation of the conventional hard switching apparatus 600 can be divided in 6 stages according to the stage of the switches M1 and M2 in one period. Each stage will be described in the following article.
When 0xe2x89xa6txe2x89xa6t1:xe2x80x83xe2x80x831.
When 0xe2x89xa6txe2x89xa6t1, the switches M1, and M2 are turned off and the node a voltage is 0.
When t1xe2x89xa6txe2x89xa6t2:xe2x80x83xe2x80x832.
The switch M1 is turned on and the switch M2 is turned off when t1xe2x89xa6txe2x89xa6t2. FIG. 8a shows the equivalent circuit of the conventional hard switching apparatus 600 when the switch M1 is turned on and the switch M2 is turned off. The equivalent circuit of the plasma display panel 304 can be represented in the form of an equivalent capacitor Cp in FIGS. 8a and 8b. The external power source is coupled to the node a directly. The node a voltage can be switched to Vd, no matter what it was before directly coupling to the external power source. The equivalent capacitor Cp is charged by the external power source through the current I1 flowing from the external power source to the equivalent capacitor Cp. The node a voltage can be raised to Vd when t=t2.
When t2xe2x89xa6txe2x89xa6t3:xe2x80x83xe2x80x833.
The switch M1 is still turned on and the switch M2 is still turned off when t2xe2x89xa6txe2x89xa6t3. When t=t2, the node a voltage is equaled to Vd. There is no current I1 flowing form the external power source to the equivalent capacitor Cp and the equivalent capacitor Cp is not charged by the external power source.
When t3xe2x89xa6txe2x89xa6t4:xe2x80x83xe2x80x834.
The switch M1 and M2 are turned off when t3xe2x89xa6txe2x89xa6t4. The voltage of node a is still Vd.
When t4xe2x89xa6txe2x89xa6t5:xe2x80x83xe2x80x835.
The switch M2 is turned on and the switch M1 is turned off when t4xe2x89xa6txe2x89xa6t5. FIG. 8b shows the equivalent circuit of the conventional hard switching apparatus 600 when the switch M2 is turned on and the switch M1 is turned off. The node a is coupled to the ground directly. The node a voltage Va can be switched to 0, no matter what it was before coupling to the ground. The equivalent capacitor Cp is discharged through the current I2 flowing from the equivalent capacitor Cp to the ground. The voltage of node a can be lowered to 0 when t=t5.
When t5xe2x89xa6txe2x89xa6t6:xe2x80x83xe2x80x836.
The switch M1 is still turned off and the switch M2 is still turned on when t5xe2x89xa6txe2x89xa6t6. When t=t6, the voltage of node a is 0. There is no current I1 flowing form the external power source to the equivalent capacitor Cp.
In this manner, the operation of the conventional hard switching apparatus 600 in one period has been accomplished.
FIG. 9 shows the diagram of the conventional bootstrap apparatus for driving the address electrode of the plasma display panel 900. The conventional bootstrap apparatus 900 includes two switches (M1 and M2), a diode (D1), a resistance (R), and a capacitor (C). The external power source is coupled to the conventional bootstrap apparatus 900 for applying the driving voltage Vd. The driving voltage of the conventional bootstrap apparatus 900 applied by the external power source can be reduced to Vd/2, instead of Vd. A signal control apparatus 902 is coupled to the conventional bootstrap apparatus 900 in the node a. The plasma display panel 904 is coupled to the signal control apparatus 902.
FIG. 10 shows the timing chart of the gate to the source voltage (Vgs) of M1 (Vg1), and M2 (Vg2), and the voltage of the node a (Va). The operation of the conventional bootstrap apparatus 900 can be controlled by controlling the ON and the OFF stage of the switches, M1 and M2, periodically. The operation of the conventional bootstrap apparatus 900 can be divided in 4 stages according to the stage of the switches M1 and M2 in one period. Each stage will be described in the following article.
When t1xe2x89xa6txe2x89xa6t2:xe2x80x83xe2x80x831.
When t=t1, the voltage of node a is 0 and the switch M2 can be turned on. Therefore, the diode D1 can be turned on because of the forward bias voltage Vd/2. The node a is coupled to the external power source directly in this manner. The node a voltage Va can be switched to Vd/2 by the external power source. The capacitor (C) can be charged by the external power source until the capacitor voltage is Vd/2.
When t2xe2x89xa6txe2x89xa6t3:xe2x80x83xe2x80x832.
When t=t2, the node a voltage is Vd/2 and the switch M2 can be turned off. The switches M1 and M2 are turned off and the node a voltage Va is still Vd/2.
When t3xe2x89xa6txe2x89xa6t4:xe2x80x83xe2x80x833.
When t=t3, the node a voltage is Vd/2 and the switch M1 can be turned on. The node a voltage Va is switched again from Vd/2 to Vd by the external power source. The capacitor (C) can be charged continuously by a current flowing form the external power source to the capacitor (C) through the switch M1 and the resistor (R).
When txe2x89xa7t4:xe2x80x83xe2x80x834.
When t=t4, the node a voltage Va is Vd and the switch M1 can be turned off. The capacitor (C) can be discharged and the node a voltage Va can be lowered to 0.
In this manner, the operation of the conventional bootstrap apparatus 900 in one period has been accomplished.
Each of the conventional address electrode driving apparatus of the plasma display panel has the following disadvantages respectively. The conventional address electrode driving apparatus needs more devices than the conventional hard switching apparatus and the conventional bootstrap apparatus. Therefore, the cost of manufacturing the conventional address electrode driving apparatus is higher than manufacturing the other two conventional address electrode driving apparatus. Since the conventional address electrode driving apparatus includes four switches, the driving method of the conventional address electrode driving apparatus is more complicated than the other two conventional address electrode driving apparatus. In addition, zero voltage switching (ZVS) is more difficult for these three conventional address electrode driving apparatus. What is called the zero voltage switching is that the drain to the source voltage (Vds) of the switch is zero when the stage of the switch is switched. In this manner, there will be no switching current between the drain electrode and the source electrode when the stage of the switch is switched. The power loss of the switch can be decreased. In addition, the electromagnetic interference (EMI) problem would be serious if the drain to the source voltage (Vds) of the switch is not zero as switching. Therefore, the total power loss can be decreased and the electromagnetic interference problem can be solved if the zero voltage switching can be accomplished. To sum up, the disadvantages of these three conventional address electrode driving apparatus are that the manufacturing cost is high, the driving method is complicated, the power loss is large, and the electromagnetic interference problem is serious.
The device needed is one in which the manufacturing cost is lower and the driving method is easier when comparing the conventional hard switching apparatus to the conventional address electrode driving apparatus. Additionally, the conventional hard switching apparatus must serially connect to the resistor (R) in order to adjust the rising time and the falling time of the node a voltage. Therefore, there will be a current flowing through the resistor (R) when the node a voltage Va is changed. The power loss is increased in the form of dissipating heat. The operation temperature can be increased in this manner. Therefore, the operation of the plasma display panel can be affected.
The driving voltage applied by the external power source in the conventional bootstrap apparatus is only a half of the other two conventional address electrode driving apparatus. However, zero voltage switching cannot be accomplished, and the power loss and the electromagnetic interference cannot be avoided when operating the conventional bootstrap apparatus. In addition, the conventional bootstrap apparatus also includes a resistor (R). Therefore, the power loss in the form of dissipating heat is increased also. The operation of the plasma display panel can be affected in this manner.
It is therefore an object of the invention to provide an improved and simplified apparatus for driving the address electrode of the plasma display panel so as to achieve the following objectives: first, to decrease the cost of the driving apparatus; second, to simplify the driving method of the driving apparatus; third, to decrease the power loss of the driving apparatus; and fourth, to decrease the problem of electromagnetic interference.
The invention achieves the above-identified objects by providing a new apparatus for driving the address electrode of the plasma display panel and the method thereof. The driving apparatus is coupled to a signal control circuit of the address electrode in a first node. Additionally, a power source for applying a driving voltage is coupled to the driving apparatus. The driving apparatus comprises a first switch, a first diode, a first capacitor, a second switch, a second diode, a second capacitor, a third capacitor, and a first inductance. The first switch is coupled to the power source and the first node, respectively. The first diode is coupled in parallel to the first switch. The first capacitor is coupled in parallel to the first switch. The second switch is coupled to the first node and a ground node, respectively. The second diode is coupled in parallel to the second switch. The second capacitor is coupled in parallel to the second switch. The third capacitor is coupled to the second node and the first node. The first inductance is coupled to the third capacitor and a second node, respectively.